1. Field of the Invention
This invention relates generally to electrical switching apparatus for electric power distribution systems and more particularly to such apparatus having insulative covers.
2. Background Information
Electrical switching apparatus used in electric power distribution systems include such devices as circuit breakers, network protectors, disconnect switches and transfer switches. Disconnect switches and transfer switches are often similar to circuit breakers but without the protective features. They are used to isolate loads and draw power from alternative sources, respectively.
Circuit interrupters such as circuit switching devices and circuit breakers are well known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload, and relatively high level short circuit conditions. Network protectors perform the function of circuit breakers and additional protective functions for networks within a distribution system.
Operator safety and control component grounding are critical issues with all of these switching devices. Many such devices are in metal cabinets or enclosures which are connected to ground to protect operators and provide equipment grounding. The metal frame and metal cover for such circuit breakers has provided a grounded dead front cover to meet these requirements. Newer circuit breakers and switches having insulative, molded plastic frames and covers do not provide a grounded front. The molded covers on such circuit breakers also do not provide a shield for electromagnetic forces that might adversely affect instrumentation in the circuit breakers or switches.
There is a need for a means to provide grounding and EMF shielding for low voltage circuit breakers having molded plastic covers on them.